1. Technical Field
The present invention relates to a method for manufacturing copper nanoparticles using microwaves.
2. Description of the Related Art
In response to demands for electronic components with miniaturization and high-densification, needs for metal patterning in a thin film using inkjet or formation of microwiring on a substrate have been increased. To implement this, it is necessary to produce conductive ink which is made from nano size of copper particles having a uniform shape, a narrow distribution of particles and an excellent dispersibility.
There are various methods of producing copper nanoparticles, such as mechanical grinding method, co-precipitation method, spray, sol-gel method, electro-deposition method, and microemulsion method, etc. In case of producing metal nanoparticles by the co-precipitation method widely used, it is impossible to control size, shape, size distribution of particles. In case of producing by the electro-deposition method and sol-gel method, it is difficult to produce in mass production and production cost is high. Also, in case of producing by the microemulsion method, it is easy to control size, shape, size distribution of particles, however, it is not suitable for practical use as the production process is complicated.
Recently, there is an attempt to producing copper nanoparticles using the wet reduction process. A partial reduction method using hydrazine has been suggested as a proper means in production of copper particles with particle size of 0.1-100 μm.
Japanese patent publication No. 02-294414 suggested a method for producing copper particles including adding an alkali hydroxide and a reducing sugar to a copper salt solution in the presence of one or more compound selected from group consisting of amino acid and its salt, ammonia and its ammonium salt, organic amine and dimethyl glyoxime and precipitating the copper oxide particles; and subsequently reducing the copper oxide particles with hydrazine.
Also, Korean patent publication No. 2005-3169 suggested a method for preparing 0.3-4 μm size of copper particles including preparing an aqueous solution of a copper salt complex by mixture an aqueous solution of a copper salt with ammonia solution; and reducing the result solution with ascorbic acid to obtain copper powder, wherein a surfactant is added to control the nucleus size and growth of particles.
Japanese patent publication No. 2004-353038 suggested a synthetic method using microwave for preparing silver ultrafine particles with size of less than 10 nm, including dispersing a fatty acid metal salt into a reductive organic alcohol solvent and irradiating the mixture to reduce from metal ions.
Copper particles produced by the above-mentioned wet method were characterized that the particle size distribution is small or the particle size is uniform, however, they have actually a broad particle size distribution and have not provided the formation of small and uniform particles with size less than 100 nm. Also, there is no description regarding the synthesis of copper nanoparticles by employing microwaves.